This is what the fuel gauge in our longterm 2005 VW Jetta TDI looks like when the tank is filled to the tippy-top. I know this because I just overfilled the tank and took this crappy cellphone picture.
Here's how it went down. I set the pump nozzle at the slowest fill setting until the pump clicked off, waited a bit and then topped it once, slowly (as per our standard filling procedure). The needle still sat here, just below full. I waited a minute or so for any gauge damping to settle out. It never happened.
Then I recalled that the Jetta had some filling issues way back when and figured it was reading below full because it actually wasn't full. I don't drive this car much so I'm not really up to speed with its idiosyncracies.
So I manually topped it off again. Slowly and carefully. It took a smidge and clicked off again. I re-checked the gauge. Same position, even after waiting another minute.
Then I gave it another tiny fraction of fuel and bam, a trickle of fuel ran out the filler neck. Dammit! I don't think this is what they had in mind when they said biodiesel was eco-friendly.
Even a few miles down the road, the gauge didn't read any fuller than what you see here. Lesson learned...
Jason Kavanagh, Engineering Editor @ 67,670 miles.
cx7lover says:
04:12 PM, 02/26/09
Wasn't this fixed?
kurtamaxxxguy says:
05:07 PM, 02/26/09
Some cars don't do well with topping off. Top-off of Subarus can flood their charcoal emissions filter, leading to emission and check-engine light issues.
desmolicious says:
05:13 PM, 02/26/09
In the blogs it mentions having to access a tab in the fuel filler neck in order to be able to fill it up all the way.
Or sumfink like that.
desmolicious says:
05:17 PM, 02/26/09
Here you go:
http://blogs.edmunds.com/roadtests/2008/05/2005-volkswagen-jetta-tdi-reserve-tank-fill-up.html#more
clarkma5 says:
05:17 PM, 02/26/09
I've stopped topping off my GTI, it doesn't seem to make any difference. My fuel gauge tends to get pegged for the first 30 miles, then goes down at the rate of about 40 miles per 8th of a tank for the first half and then about 35 miles per 8th of a tank for the second half, and when it gets to empty it still has 3 gallons left. That's just how it goes...
jerome81 says:
10:14 PM, 02/26/09
does the MKV GTI have that same tab in the fuel filler of the TDIs?
Beyond that, what is the point of that system??
Might be nice to squeeze that extra bit into my GTI on fillups...
jahfakin says:
01:14 AM, 02/27/09
how much gallons are you putting in? are you 'venting'?
dougtheeng says:
04:45 AM, 02/27/09
Did you use the venting feature?
txmatt1 says:
07:07 AM, 02/27/09
You'd also have to be 3 feet tall to actually look at the instrument cluster from that exaggerated angle while sitting in the driver's seat.
karjunkie says:
08:00 AM, 02/27/09
kurtamaxxxguy makes a very good point. Why risk damaging your EVAP system just to squeeze a little more diesel fuel into the tank? How many refueling stops will you avoid by adding a few more squirts of diesel fuel?????
fadetoblackii says:
08:02 AM, 02/27/09
What is 'venting'?
pengwin says:
08:19 AM, 02/27/09
i dont think Mk5s' reserve tanks have to be manually filled
vwthing1 says:
08:43 AM, 02/27/09
A couple of things:
1) diesel fuel foams when it is pumped into the tank... even on the slowest flow rate of most nozzles. Many TDI'ers wanting a completely full tank will let the nozzle to auto-click off, wait 5 or so minutes for the foam to settle (check oil, buy a soda, clean the windows, etc.), then resume pumping slowly. It takes longer, but when you only have to fuel up every 6-700 miles, it's not so bad.
2) AFAIK, there's no EVAP system on the TDI cars-- diesel fuel doesn't evaporate as easily as gas (note the oily film of unevaporated fuel on the diesel pump and on the ground adjacent the pump). So, there's no harm to top off.
3) as others have said... use the vent... or go over to TDIclub.com and figure out how to remove the vent.
warren_w says:
09:33 AM, 02/27/09
There's a black tab on the inside of the filler neck in about the 9 0'clock postion. If you press this in with side of the fuel pump nozzle you can usually get in an extra 2-3 gallons after the pump has clicked off. It is part of the evaporative system for the gas cars. Since this is not a worry with diesel you can use this extra space to extend your range (~120 miles).
I don't beleive that the MK5 cars have this feature. I can usually get about 16 gallons into my Golf once the fuel light comes on using "venting".
Removing the vent isn't hard. You remove the rubber surrounding the fuel filler neck. Press a tab on the under side of the venting piece. Slide out the piece, remove the spring and a plunger, then push it back in. Put back the rubber surround. Takes maybe 15 minutes, tops.
altimadude00 says:
11:21 AM, 02/27/09
I'm surprised that no one has said that the gauge might be faulty. I guess nothing from Germany can be faulty or break.
Oh wait, the M3 is slowly falling apart. Nevermind.
Mitlov says:
12:02 PM, 02/27/09
The fuel gauge on my MkIV Jetta 1.8T is just like this. To be honest, I've never worried about it or thought twice about it until this article. Life's too short to worry if the fuel gauge needle rests on "F" or just left of "F" when the tank is full.
mctdi says:
05:37 PM, 09/12/10
If you want FULL to show as FULL check this link: http://forums.tdiclub.com/showthread.php?p=1116000
But then you low fuel light will come on, with less than the factory setting of approx. 1.8 gal.